Interaction of constituents of MDT regimen for leprosy with Mycobacterium leprae HSP18: impact on its structure and function

Abstract

Mycobacterium leprae, the causative organism of leprosy, harbors many antigenic proteins, and one such protein is the 18-kDa antigen. This protein belongs to the small heat shock protein family and is commonly known as HSP18. Its chaperone function plays an important role in the growth and survival of M. leprae inside infected hosts. HSP18/18-kDa antigen is often used as a diagnostic marker for determining the efficacy of multidrug therapy (MDT) in leprosy. However, whether MDT drugs (dapsone, clofazimine, and rifampicin) do interact with HSP18 and how these interactions affect its structure and chaperone function is still unclear. Here, we report evidence of HSP18-dapsone/clofazimine/rifampicin interaction and its impact on the structure and chaperone function of HSP18. These three drugs interact efficiently with HSP18 (having submicromolar binding affinity) with 1 : 1 stoichiometry. Binding of these MDT drugs to the 'α-crystallin domain' of HSP18 alters its secondary structure and tryptophan micro-environment. Furthermore, surface hydrophobicity, oligomeric size, and thermostability of the protein are reduced upon interaction with these three drugs. Eventually, all these structural alterations synergistically decrease the chaperone function of HSP18. Interestingly, the effect of rifampicin on the structure, stability, and chaperone function of this mycobacterial small heat shock protein is more pronounced than the other two MDT drugs. This reduction in the chaperone function of HSP18 may additionally abate M. leprae survivability during multidrug treatment. Altogether, this study provides a possible foundation for rational designing and development of suitable HSP18 inhibitors in the context of effective treatment of leprosy.

Purification, characterization and functional site prediction of the vaccinia-related kinase 2A small transmembrane domain

“…IV. Thermal stability, tertiary structural characteristics and surface hydrophobicity analysis of GVTMD and VTMD proteins Determination of Thermal stability Thermal stability of GVTMD, VTMD and GST proteins was compared by plotting the far-UV CD data at 208 nm in a temperature range of 20°C–90°C [30] . Thermal stability of GVTMD, VTMD and GST only proteins (17.5 μM in PBS buffer, pH 7.0) was assessed by monitoring the CD spectrum with increasing temperature.…”

“…Thermal stability of GVTMD, VTMD and GST proteins was compared by plotting the far-UV CD data at 208 nm in a temperature range of 20°C–90°C [30] .…”

Impact of nanoparticles on amyloid β-induced Alzheimer’s disease, tuberculosis, leprosy and cancer: a systematic review

“…Leprosy is treated by the Multidrug therapy (MDT) regimen introduced by the WHO in the 1980s. Despite the success of MDT in the treatment of leprosy, poor patient–drug compliance has been observed over the years due to the adverse side effects of these MDT drugs, namely rifampicin, dapsone and clofazimine [ 93 ]. These drugs, though highly effective against leprosy, are classified as Class II drugs according to the Biopharmaceutics Classification System as they have low water solubility and oral drug bioavailability [ 94 ].…”

“…The effect of ∼20 nm citrate capped silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) on HSP18, an 18 kDa immunodominant small heat shock protein belonging to M. leprae was tested. This small heat shock protein is also responsible for the growth and survival of this pathogen in host macrophages by virtue of its chaperone function [ 93 , 107 ]. Fluorometric characterization of binding of these two nanoparticles with HSP18 revealed the nature/stoichiometry of binding i.e., one silver nanoparticle/gold nanoparticle binding per subunit of HSP18 with binding affinity in the submicromolar range [ 108 ].…”

The perennial pursuit for an ideal anti-leprosy treatment

“…5,6 Although only bacteriostatic to Mycobacterium leprae, the resistance among the bacilli for clofazimine is practically unknown, and continuous therapy with clofazimine results in sustained inhibition of bacterial proliferation. 7 Dapsone was among the first drugs utilized for the management of leprosy, and continues to be a component of WHO-MDT even though it is mildly bactericidal for M. leprae. A single dose of dapsone gives a blood concentration of 1.5 μg/ml, 500 times the MIC of 0.003 μg/ml for M. leprae.…”